Study On The Electrochemical Stability And Factors Of Influence To Promote The Degradation Of Phenol With TiO₂/ACF- Graphite Electrode

Phenolic wastewater is one kind of refractory organic wastewater which is widely from coal chemical industry, oil refining, coking, dyes, food, pesticide, medicine, polymer synthesis and some other fields. Phenolic wastewater, with high toxicity, is difficult to degrade. High attention was paid to the pollution caused by the phenolic wastewater.Therefore, the treatment of phenolic wastewater has also become the focus of the studies.Electrochemical catalysis, which is environmental friendly, has been used to refresh the wastewater. In this paper, the graphite plate enveloped with titanium dioxide(TiO2)loaded activated carbon fiber felt(ACF) was used as anode and a graphite plate was used as cathode. Phenol simulated wastewater is the research object of this experiment. Based on previous laboratory studies, the phenol degradation process was further studied including reasons for the lack of the stability of the electrode and ways to improve it. These can lay the theoretical foundation for the practical application. The main contents are as follows:In order to strengthen the solidity of TiO2 loading, nano-TiO2 particles were generated in situ in the micropores inside the ACF by "bottle in a ship" method to resist the impact of shear flow. The degradation of phenol, with an initial concentration of 100mg/L, was operated in optional experimental conditions determined in primary work. Compared with primary studies of our research group, phenol degradation rate was increased and the service life of TiO2/ACF electrode was prolonged.The unstable preparation mode of TiO2 was not the only reason for the failure of TiO2/ACF electrode. A variety of intermediate products, such as hydroquinone, catechol and benzoquinone, were found during the degradation process. These intermediateproducts take part in the competition of the occupation of adsorption and catalytic active sites with phenol. And these may be the key factors to the stability to the electrode. In this paper, the influence of these intermediate products on the competitive adoption and electrochemical degradation of phenol was fully discussed. Studies have shown that intermediate products could greatly decline the maximum adsorption quality and adsorption rate of phenol on the TiO2/ACF electrode. In the solution consisted of these four organic compounds, the adsorption rate of phenol was decreased sharply while the adsorption rate of benzoquinone was the fastest. Hydroquinone could be oxidized to benzoquinone at anode, while benzoquinone could also be reduced to hydroquinone at cathode when the concentration of benzoquinone was high enough. The balance between benzoquinone and hydroquinone in the electrochemical system could be effectively braked when electrolytic cell is separated into two part by the membrane.For the real application of TiO2/ACF electrode, several methods for improving the electrochemical system have been adopted: firstly, air was introduced. Oxygen might cause series reaction at cathode generating oxygen radicals and hydrogen peroxide. As the result,the degradation of phenol was increased, but the accumulations of intermediate products were even more. Secondly, hydrogen peroxide(H2O2) was adding in the system. Hydrogen peroxide could be catalyzed by TiO2/ACF electrode and generate hydroxyl radical(·OH)10 times as the amount without H2O2. The degradation rate of phenol was increased, while the accumulations of intermediate products were significantly declined. Therefore, the electrochemical system with TiO2/ACF electrode could be promoted in the practical applications.